Methods and Devices for Knee Joint Replacement with Anterior Cruciate Ligament Substitution

ABSTRACT

Methods and devices are provided for knee joint replacement with anterior cruciate ligament (ACL) substitution. Generally, the methods and devices can allow a knee joint to be partially or totally replaced in conjunction with substitution of the knee joint&#39;s ACL. In one embodiment, a knee replacement prosthesis can include a medial or lateral femoral implant, a femoral intercondylar notch structure, a medial or lateral tibial insert, and an ACL-substitution member. The ACL-substitution member can be configured to engage with the femoral intercondylar notch structure during a full range of knee motion and/or during only early knee flexion.

CROSS REFERENCES

This application is a continuation of U.S. patent application Ser. No.14/630,421 filed Feb. 24, 2015, which is a continuation of U.S. patentapplication Ser. No. 13/547,383 filed Jul. 12, 2012, now U.S. Pat. No.9,005,299, which claims priority to U.S. Provisional Patent ApplicationNo. 61/507,434 entitled “Methods and Devices for Knee Joint Replacementwith Anterior Cruciate Ligament Substitution” filed Jul. 13, 2011, whichis hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to methods and devices for knee jointreplacement with anterior cruciate ligament (ACL) substitution, and inparticular to methods and devices for substituting a prosthesis for anACL.

BACKGROUND OF THE INVENTION

FIG. 1 illustrates a typical knee joint including a femur 1 and a tibia3, shown with healthy femur cartilage 5 and healthy tibia cartilage 7.The knee joint includes three primary elements; a medial tibiofemoraljoint, a lateral tibiofemoral joint, and a central patellofemoral joint.Joint trauma or diseases such as osteoarthritis and rheumatoid arthritiscan cause severe damage to one or more of these elements. In a casewhere one or more of the knee elements are traumatized or diseased,while the other one or two knee elements are healthy, the traumatized ordiseased element(s) can be replaced in a partial knee replacementsurgical procedure. In a case where all three primary elements aretraumatized or diseased, all three elements can be replaced in a totalknee replacement surgical procedure.

In both partial and total knee replacement surgical procedures, thetraumatized or diseased ones of the knee's bony surfaces, e.g., femur,tibia, and patella, can be replaced by prosthetic components. The knee'ssoft-tissue structures, particularly ligaments surrounding the kneejoint, can be largely left intact. The knee's major ligament structuresinclude medial and lateral collateral structures, and anterior andposterior cruciate ligaments. These ligamentous structures play asignificant role in controlling the motion and stability of a kneejoint. With regards to the cruciate ligaments, the posterior cruciateligament (PCL) is generally present and well-functioning in patientsundergoing partial or total knee replacement surgery. However, in atleast some patients, the anterior cruciate ligament (ACL) can be absentor non-functional at surgery due to prior trauma or gradual degradation.

Traditional partial knee replacement prostheses have no mechanism forsubstitution of ACL function. Consequently, patients with an absent ornon-functional ACL may end up receiving total joint replacement, whichis a generally more invasive procedure than partial knee replacement andwhich replaces the healthy element(s) of the patient's knee.Alternatively, instead of total knee replacement, patients with anabsent or non-functional ACL may undergo additional surgery prior to apartial knee replacement surgical procedure to reconstruct the ACL, suchas with a soft tissue graft.

In traditional total knee replacement surgical procedures, patientsreceive a type of prosthesis, e.g., a cruciate retaining (CR) typeimplant, that allows the present and well-functioning PCL to beretained. However, even for patients who have a functional ACL, the ACLis traditionally resected during surgery prior to implantation of a CRtype implant because of difficulty in achieving optimal soft-tissuebalancing and component placement with both the ACL and PCL present.However, traditional CR prostheses have no mechanism for substitution ofthe ACL function. Consequently, following CR prosthesis implantation,the knee shows abnormal motion patterns characterized by features suchas reduced tibial internal rotation and paradoxical anterior femoraltranslation.

Accordingly, there remains a need for improved knee prostheses andmethods for treating disease and trauma affecting the knee.

SUMMARY OF THE INVENTION

The present invention generally provides methods and devices for kneejoint replacement with anterior cruciate ligament (ACL) substitution. Inone aspect, a medical device is provided that includes a tibial implant,a femoral implant, and a post. The tibial implant has an inferiorsurface and an opposite, superior surface. The inferior surface isconfigured to be fixed to a tibia of a patient. The femoral implant ismateable to the tibial implant and has an inferior surface and anopposite, superior surface. The superior surface of the femoral implantis configured to be fixed to a femur of the patient, and the tibialimplant is configured to articulate relative to the femoral implant whenthe tibial implant is fixed to the tibia and the femoral implant isfixed to the femur. The post extends from the superior surface of thetibial implant near an edge thereof. The post is configured to besubstantially centered on the tibia when the tibial implant is fixedthereto such that the post simulates an ACL when the tibial implant isfixed to the tibia and the femoral implant is fixed to the femur.

The tibial implant can have a variety of configurations. The tibialimplant can have a medial compartment configured to be seated on amedial surface of the tibia with a first portion of the tibial implantbeing seated on or over the tibia's medial surface and a second,substantially smaller portion of the tibial implant being seated on orover the tibia's lateral surface. The tibial implant can have a lateralcompartment configured to be seated on a lateral surface of the tibiawith a first portion of the tibial implant being seated on or over thetibia's lateral surface and a second, substantially smaller portion ofthe tibial implant being seated on or over the tibia's medial surface.The tibial implant can have medial and lateral compartments. The lateralcompartment can be configured to be seated on a lateral surface of thetibia such that the lateral surface is substantially covered by thelateral compartment. The medial compartment can be configured to beseated on a medial surface of the tibia such that the medial surface issubstantially covered by the medial compartment.

The post can have a variety of configurations. The post can beasymmetric in sagittal, coronal, and transverse planes. The post can beintegrally formed with the tibial implant, or the post can be a discreteelement configured to couple to the tibial implant.

In some embodiments, the device can include a femoral notch structurecoupled to the femoral implant. The femoral notch structure can beconfigured to prevent the post from impinging on a lateral surface ofthe femur through a full range of knee flexion when the tibial implantis fixed to the tibia and the femoral implant is fixed to the femur. Thepost can be configured to articulate relative to the femoral notchstructure.

In another aspect, a medical method is provided that includes implantinga partial knee prosthesis in a patient to replace one of a medialtibiofemoral joint of a knee and a lateral tibiofemoral joint of theknee such that an inferior surface of a tibial implant of the kneeprosthesis faces a tibia of the knee, a superior surface of the tibialimplant faces an inferior surface of a femoral implant of the kneeprosthesis, a superior surface of the femoral implant faces a femur ofthe knee, and a post extending from the superior surface of the tibialimplant functions as a substitute for an ACL of the knee. The tibialimplant and the post are configured to articulate relative to thefemoral implant, and the post does not impinge on a lateral surface ofthe femur when the post articulates relative to the femoral implantthrough a full range of knee flexion.

In another embodiment, a medical method is provided, that includesimplanting a total knee prosthesis in a patient to replace both of amedial tibiofemoral joint of a knee and a lateral tibiofemoral joint ofthe knee such that an inferior surface of a tibial implant of the kneeprosthesis faces a tibia of the knee, a superior surface of the tibialimplant faces an inferior surface of a femoral implant of the kneeprosthesis, a superior surface of the femoral implant faces a femur ofthe knee, and a post extending from the superior surface of the tibialimplant functions as a substitute for an ACL of the knee. The tibialimplant and the post are configured to articulate relative to thefemoral implant, and the post does not impinge on a lateral surface ofthe femur when the post articulates relative to the femoral implantthrough a full range of knee flexion.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 (PRIOR ART) is a perspective view of a typical normal human knee;

FIG. 1A is view of one embodiment of a knee prosthesis having anACL-substitution member including a plurality of discrete pieces;

FIG. 1B is a top view of one embodiment of a knee prosthesis;

FIG. 1C is a sagittal cross-sectional view of the knee prosthesis ofFIG. 1B;

FIG. 1D is a coronal cross-sectional view of the knee prosthesis of FIG.1B;

FIG. 1E is a side view of one embodiment of a knee prosthesis includingan ACL-substitution member and a femoral notch structure configured toengage through a full range of knee motion;

FIG. 1F is top, partial view of one embodiment of a tibial insert;

FIG. 1G is coronal section view B-B of the tibial insert of FIG. 1F anda femoral implant;

FIG. 2 is a posterior perspective view of one embodiment of a medialknee prosthesis attached to a tibia arid a femur;

FIG. 3 is a posterior perspective view of one embodiment of a lateralknee prosthesis attached to a tibia and a femur;

FIG. 4 is a top view of a tibial insert of the medial knee prosthesis ofFIG. 2 seated on the tibia;

FIG. 5 is a side perspective view of the tibial insert of FIG. 4;

FIG. 6 is a top view of a tibial insert of the lateral knee prosthesisof FIG. 3;

FIG. 7 is a side view of the tibial insert of FIG. 6;

FIG. 8 is a perspective view of the tibial insert of FIG. 6;

FIG. 8A is a side view of one embodiment of a knee prosthesis includinga tibial post located substantially anterior to tibial center;

FIG. 8B is top view of the femoral component of the prosthesis of FIG,8A;

FIG. 8C is a top view of the prosthesis of FIG. 8A;

FIG. 9 is a top view of the tibial insert of the lateral knee prosthesisof FIG. 3 seated on the tibia;

FIG. 10 is another top view of the tibial insert of FIG. 9;

FIG. 11 is a perspective view of one embodiment of a medial kneeprosthesis attached to a tibia, the medial knee prosthesis including apost gradually blending into a tibial insert of the prosthesis;

FIG. 12 is a schematic view of one embodiment of a lateral kneeprosthesis including a tibial post and a tibial insert, the tibial posthaving a lateral edge extending back to a posterior edge of the tibialinsert;

FIG. 13 is a top view of the medial knee prosthesis of FIG. 2 attachedto the tibia;

FIG. 13A is a top view of an embodiment of a lateral knee prosthesisattached to a tibia;

FIG. 14 is a side perspective view of the medial knee prosthesis of FIG.13;

FIG. 14A is a side perspective view of the lateral knee prosthesis ofFIG. 13A;

FIG. 15 is a top view of one embodiment of a medial knee prosthesisattached to a tibia, the prosthesis including a discrete femoral notchstructure and a discrete femoral implant;

FIG. 16 is a side perspective view of the medial knee prosthesis of FIG.15;

FIG. 17 is a perspective view of one embodiment of a lateral kneeprosthesis in an extended or closed position;

FIG. 18 is a perspective view of the prosthesis of FIG. 17 in a flexedor open position;

FIG. 19 is a top view of one embodiment of a lateral knee prosthesisattached to a tibia, the prosthesis including a post having a roundedtop;

FIG. 20A is aside schematic view of the prosthesis of FIG. 19;

FIG. 20B is a side schematic view of one embodiment of a lateral kneeprosthesis attached to a tibia, the prosthesis including a post havingan angled or chamfered top;

FIG. 20C is a side view of an embodiment of a bone shaping tool;

FIG. 20D is a top view of another embodiment of a bone shaping tooladjacent to an embodiment of a femoral component;

FIG. 20E is a top view of an embodiment of a femoral trial componentthat includes one or more guiding slots;

FIG. 20F is a side view of an embodiment of a trial tibial insert thathas a larger size than an embodiment of a tibial insert;

FIG. 20G is a side view of the trial tibial insert of FIG. 20Fpositioned adjacent a femoral bone and an embodiment of a femoralcomponent;

FIG. 21 are top schematic views of one embodiment of a lateral kneeprosthesis including a tibial post and a femoral intercondylarstructure, the post, an anterior surface, and a lateral surface of thefemoral intercondylar structure having concentric circular profiles;

FIG. 21A is top, partial view of one embodiment of a prosthesisincluding a tibial post including angled cuts;

FIG. 21B is a perspective, partial view of the prosthesis of FIG, 21A;

FIG. 21C is a sagittal section view A-A of the tibial insert of FIG.21A;

FIG. 21D is a coronal section view B-B of the tibial insert of FIG. 21A;

FIG. 22 is a top view of one embodiment of a medial knee prosthesisattached to a tibia, the prosthesis having a convex tibial post and aconvex femoral intercondylar notch;

FIG. 23 is a schematic, sagittal plane cross-sectional view of theprosthesis of FIG. 22;

FIG. 24 is a schematic, sagittal plane cross-sectional view of oneembodiment of a medial knee prosthesis, the prosthesis having a concavetibial post and a convex femoral intercondylar notch;

FIG. 25 is a schematic, sagittal plane cross-sectional view of oneembodiment of a medial knee prosthesis, the prosthesis having a convextibial post and a concave femoral intercondylar notch;

FIG. 26 is a schematic, sagittal plane cross-sectional view of oneembodiment of a medial knee prosthesis, the prosthesis having a flattibial post and a convex femoral intercondylar notch;

FIG. 27 is a schematic, sagittal plane cross-sectional view of oneembodiment of a medial knee prosthesis, the prosthesis having a convextibial post and a flat femoral intercondylar notch;

FIG. 28 is a top view of one embodiment of a lateral knee prosthesisattached to a tibia, the prosthesis having a concave tibial post and aconvex femoral intercondylar notch;

FIG. 29 is a schematic, coronal plane cross-sectional view of theprosthesis of FIG. 28;

FIG. 30 is a schematic, coronal plane cross-sectional view of oneembodiment of a lateral knee prosthesis attached to a tibia, theprosthesis having a flat tibial post and a flat femoral intercondylarnotch;

FIG. 31 is a schematic, coronal plane cross-sectional view of oneembodiment of a lateral knee prosthesis attached to a tibia, theprosthesis having a convex tibial post and a convex femoralintercondylar notch;

FIG. 32 is a schematic, coronal plane cross-sectional view of oneembodiment of a lateral knee prosthesis attached to a tibia, theprosthesis having a flat tibial post and a convex femoral intercondylarnotch;

FIG. 33 is a schematic, coronal plane cross-sectional view of oneembodiment of a lateral knee prosthesis attached to a tibia, theprosthesis having a convex tibial post and a flat femoral intercondylarnotch;

FIG. 34 is a top perspective view of one embodiment of a total kneereplacement prosthesis;

FIG. 35 is a perspective view of one embodiment of a total kneereplacement prosthesis attached to a femur, the prosthesis being in anextended or closed position and including a femoral notch structure;

FIG. 36 is a perspective view of the prosthesis of FIG. 35 not attachedto bone and in a flexed or open position;

FIG. 37 is a perspective view of the prosthesis of FIG. 34 attached to afemur and showing a representation of a PCL ligament;

FIG. 38 is a perspective view of the prosthesis of FIG. 37 not attachedto bone and with the representation of the PCL ligament in positionscorresponding to different knee flexion angles;

FIG. 39 is a top view of a tibial implant of the prosthesis of FIG. 34;

FIG. 40 is a side view of the tibial implant of FIG. 39;

FIG. 41 is a perspective view of the tibial implant of FIG. 39;

FIG. 42 is a top view of the tibial implant of FIG. 39;

FIG. 43 is another top view of the tibial implant of FIG. 39;

FIG. 44 is a perspective view of one embodiment of a total kneereplacement prosthesis including a post gradually blending into a tibialinsert of the prosthesis;

FIG. 45 is a schematic view of one embodiment of a total kneereplacement prosthesis including a tibial post and a tibial insert, thetibial post having a lateral edge extending back to a posterior edge ofthe tibial insert;

FIG. 46 is a perspective view of one embodiment of a total kneereplacement prosthesis attached to a femur and having a post with aheight configured to avoid impingement with the lateral femoral condyle;

FIG. 47 is a top view of one embodiment of a total knee replacementprosthesis including a post having a rounded top;

FIG. 48 is a side schematic view of the prosthesis of FIG. 47;

FIG. 49 is a perspective view of one embodiment of a total kneereplacement prosthesis in an extended or closed position;

FIG. 50 is a perspective view of the prosthesis of FIG. 49 in a flexedor open position;

FIG. 51 is a top view of one embodiment of a total knee replacementprosthesis having a convex tibial post and a convex femoralintercondylar notch;

FIG. 52 is a top view of one embodiment of a total knee replacementprosthesis having a concave tibial post and a convex femoralintercondylar notch;

FIG. 53 is a schematic, coronal plane cross-sectional view of theprosthesis of FIG. 52 attached to a tibia;

FIG. 54 is a schematic, coronal plane cross-sectional view of oneembodiment of a total knee replacement prosthesis attached to a tibia,the prosthesis having a flat tibial post and a flat femoralintercondylar notch;

FIG. 55 is a schematic, coronal plane cross-sectional view of oneembodiment of a total knee replacement prosthesis attached to a tibia,the prosthesis having, a convex tibial post and a convex femoralintercondylar notch;

FIG. 56 is a schematic, coronal plane cross-sectional view of oneembodiment of a total knee replacement prosthesis attached to a tibia,the prosthesis having a flat tibial post and a convex femoralintercondylar notch;

FIG. 57 is a schematic, coronal plane cross-sectional view of oneembodiment of a total knee replacement prosthesis attached to a tibia,the prosthesis having a convex tibial post and a flat femoralintercondylar notch;

FIG. 58 is a graph showing motion of a medial flexion facet center (FFC)of a total knee replacement prosthesis as a function of knee flexionduring a simulated lunge activity for a ACL-substituted CR implant ofthe prosthesis and for a conventional CR implant;

FIG. 59 is a graph showing motion of a lateral FFC of the prosthesis ofFIG. 58 as a function of knee flexion during a simulated lunge activityfor the ACL-substituted CR implant and for a conventional CR implant;

FIG. 60 is a graph showing motion of the medial FFC of the prosthesis ofFIG. 58 as a function of knee flexion during a simulated deep kneebending activity for the ACL-substituted CR implant and for aconventional CR implant;

FIG. 61 is a graph showing motion of the lateral FFC of the prosthesisof FIG. 58 as a function of knee flexion during a simulated deep kneebending activity for the ACL-substituted CR implant and for aconventional CR implant;

FIG. 62 is a graph showing motion of the medial FFC of the prosthesis ofFIG. 58 as a function of knee flexion during a simulated chair rise/sitactivity for the ACL-substituted CR implant and for a conventional CRimplant;

FIG. 63 is a graph showing motion of the lateral FFC of the prosthesisof FIG. 58 as a function of knee flexion during a simulated chairrise/sit activity for the ACL-substituted CR implant and for aconventional CR implant;

FIG. 64 is a graph showing motion of the medial FFC of the prosthesis ofFIG. 58 as a function of knee flexion during a simulated stair ascentactivity for the ACL-substituted CR implant and for a conventional CRimplant;

FIG. 65 is a graph showing motion of the lateral FFC of the prosthesisof FIG. 58 as a function of knee flexion during a simulated stair ascentactivity for the ACL-substituted CR implant and for a conventional CRimplant;

FIG. 66 is a graph showing motion of the medial FFC of the prosthesis ofFIG. 58 as a function of knee flexion during simulated walking for theACL-substituted CR implant and for a conventional CR implant;

FIG. 67 is a graph showing motion of the lateral FFC of the prosthesisof FIG. 58 as a function of knee flexion during simulated walking forthe ACL-substituted CR implant and for a conventional CR implant;

FIG. 68 is a medial/lateral cross-sectional view of one embodiment of atibial insert of a knee prosthesis having a reduced articular surface;

FIG. 69A is a medial/lateral cross-sectional view of another embodimentof a tibial insert of a knee prosthesis having a reduced articularsurface;

FIG. 69B is a side view of the tibial insert of FIG. 69A adjacent afemur;

FIG. 70 is a medial/lateral cross-sectional view of yet anotherembodiment of a tibial insert of a knee prosthesis having a reducedarticular surface;

FIG. 71 is a medial/lateral cross-sectional view of an embodiment of atibial insert having a concave medial profile and a convex lateralprofile;

FIG. 72 is a medial/lateral cross-sectional view of an embodiment of atibial insert having an angled anterior edge;

FIG. 73 is a medial/lateral cross-sectional view of an embodiment of atibial insert of a knee prosthesis having a reduced distal femoralcondyle radius, the tibial insert shown adjacent a femur;

FIG. 74A is a side, partially transparent view of an ACL and PCLsubstituting prosthesis including a femoral component and a tibialinsert including a tibial post;

FIG. 74B is another view of the prosthesis of FIG. 74A;

FIG. 75 is a partial side cross-sectional view of an embodiment of afemoral component mated to an anterior and posterior tibial post, thefemoral component having an increased thickness and radius;

FIG. 76 is a partial side cross-sectional view of an embodiment of afemoral component mated to an anterior and posterior tibial post, thefemoral component having an increased radius;

FIG. 77 is a top view of one embodiment of a tibial post having a convexprofile, the tibial post engaged with a femoral notch having a roundedprofile;

FIG. 78 is top view and a perspective view of one embodiment of a tibialpost having a convex profile engaged with a femoral notch having aconcave profile;

FIG. 79 is a side view of one embodiment of a tibial post engaging afemoral cam;

FIG. 80A is a sagittal view of an embodiment of a tibial post that isangled posteriorly;

FIG. 80B is a sagittal view of an embodiment of a tibial post that hasan anteriorly angled anterior surface and a posteriorly angled posteriorsurface;

FIG. 81A is a top view of one embodiment of a tibial implant including amovable lateral tibial insert;

FIG. 81B is a side cross-sectional view of a portion of the tibialimplant of FIG. 81A;

FIG. 81C is a side view of an embodiment of a tibial baseplate having asubstantially flat top surface profile;

FIG. 81D is a coronal cross-sectional view of a portion of the tibialimplant of FIG. 81A;

FIG. 81E is a coronal cross-sectional view of an embodiment of a tibialimplant having a baseplate with a substantially flat profile;

FIG. 81F is a coronal cross-sectional view of an embodiment of a tibialimplant having a baseplate with a substantially convex profile;

FIG. 82A is a top view of an embodiment of a tibial implant including amovable medial tibial insert and a movable lateral insert;

FIG. 82B is a side view of an embodiment of a tibial baseplate having asubstantially flat top surface profile and opposed side rails for amedial tibial insert and opposed side rails for a lateral tibial insert;

FIG. 82C is a side view of an embodiment of a tibial baseplate having arelatively small radius convex structure on a top surface thereofconfigured to movably mate a tibial insert thereto; and

FIG. 82D is a side view of an embodiment of a tibial baseplate having arelatively large radius convex top surface thereof configured to movablymate a tibial insert thereto.

DETAILED DESCRIPTION OF THE INVENTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

Various exemplary methods and devices are provided for knee jointreplacement with anterior cruciate ligament (ACL) substitution. Ingeneral, the methods and devices can allow a knee joint to be partiallyor totally replaced in conjunction with substitution of the knee joint'sACL. In other words, when an ACL is absent, non-functional, or otherwiseneeds repair during a partial or total knee replacement surgicalprocedure, a partial or total knee replacement prosthesis can beimplanted in the same surgical procedure as an ACL substitute.Providing, a substitute for an ACL with a knee replacement prosthesiscan help reduce a number of surgical procedures needed to repair theknee and/or can help the knee's functionality approach 100% aftersurgery.

The prostheses described herein can be formed of one or more materials,such as polyolefins, polyethylene, ultra-high molecular weightpolyethylene, medium-density polyethylene, high-density polyethylene,medium-density polyethylene, highly crosslinked ultra-high molecularweight polyethylene (UHMWPE), etc. Exemplary embodiments of UHMWPEprosthesis materials and manufacturing processes are described in U.S.application Ser. No. 08/600,744 (now U.S. Pat. No. 5,879,400) filed Feb.13, 1996, entitled “Melt-Irradiated Ultra High Molecular WeightPolyethylene Prosthetic Devices;” U.S. application Ser. No. 12/333,572filed Dec. 12, 2008, entitled “Radiation And Melt Treated Ultra HighMolecular Weight Polyethylene Prosthetic Devices;” U.S. application Ser.No. 11/564,594 (now U.S. Pat. No. 7,906,064) filed Nov. 29, 2006,entitled “Methods For Making Oxidation Resistant Polymeric Material;”U.S. application Ser. No. 12/522,728 filed Apr. 5, 2010, entitled“Methods For Making Oxidation-Resistant Cross-Linked PolymericMaterials;” U.S. application Ser. No. 11/030,115 (now U.S. Pat. No.7,166,650) filed Jan. 7, 2005, entitled “High Modulus CrosslinkedPolyethylene With Reduced Residual Free Radical Concentration PreparedBelow The Melt;” U.S. application Ser. No. 12/041,249 filed Mar. 3,2008, entitled “Cross-Linking Of Antioxidant-Containing Polymers;” whichare hereby incorporated by reference in their entireties.

Generally, a knee replacement prosthesis, also referred to herein as a“knee replacement prosthesis,” a “prosthesis.” and an “implant,” caninclude a medial or lateral femoral component, also referred to hereinas a “femoral implant,” a femoral intercondylar notch structure, amedial or lateral tibial insert, also referred to herein as a “tibialimplant,” and an ACL-substitution member, also referred to herein as an“ACL-substitution member,” “ACL substituting post,” a “tibial post,” anda “post.” The femoral intercondylar notch structure can be formedintegrally with the femoral component, or the femoral intercondylarnotch structure can be a discrete element from the femoral component.The ACL-substitution member can be configured to engage with the femoralintercondylar notch structure, also referred to herein as a “femoralintercondylar notch structure” and a “femoral notch structure.” TheACL-substitution member can extend from a surface of the tibial insert,such as by being an integral part thereof, by being integrally formedwith another portion of the prosthesis, or by being a discrete elementconfigured to couple to the tibial insert. In an exemplary embodiment,the ACL-substitution member can be integrally formed with a tibialbaseplate of the prosthesis. In other exemplary embodiments, theACL-substitution member can be integrally formed with the tibial insertand extend from a tibial articular surface thereof. The ACL-substitutionmember can be a unitary or singular element, or it can include aplurality of discrete pieces. FIG. 1A illustrates an exemplaryembodiment of a prosthesis 8 having an ACL-substitution member 10including multiple pieces, e.g., an anterior piece 10 a and a lateralpiece 10 b, configured to engage with corresponding regions of thefemoral notch. For reference, a top side of FIG. 1A is an anterior sideof the prosthesis 8, and, a right side of FIG. 1A is a lateral side ofthe prosthesis 8. Thus, an anterior part 12 of the anterior piece 10 ais on a left side of FIG. 1A, and a posterior lateral part 14 of thelateral piece 10 b is on a bottom side of FIG. 1A. Exemplary embodimentsof articular surface geometry are described in Intl. App. No.PCT/US2010/059387 filed Dec. 8, 2010, entitled “Implant For RestoringNormal Range Of Flexion And Kinematics Of The Knee,” which is herebyincorporated by reference in its entirety.

Embodiments of prostheses described herein can generally be configuredto substitute the function of an ACL via engagement of the femoralintercondylar notch with the prosthesis, e.g., with the ACL-substitutionmember of the prosthesis, during a full range of knee motion, e.g., in arange of about −20° to 160° knee flexion, and/or during only early kneeflexion, e.g., in a range of about −20° to 40°. In an exemplaryembodiment, the ACL-substitution member configured to engage the femoralintercondylar notch can have a low profile, e.g., be a short post. Inanother embodiment of a prosthesis 16, shown in FIGS. 1B, 1C, and 1D, anACL-substitution member configured to engage the femoral intercondylarnotch can include a two-step eminence between the medial and lateraltibial plateau that blends smoothly with the medial and lateralarticular surfaces in the coronal and sagittal planes. Radii R1, R2, R3,R4 of the prosthesis 16 can be in a range of about 2 to 100 mm, e.g.,about 2 to 30 mm, about 5 to 25 mm, about 12 to 20 mm, about 25 to 50mm, about 55 to 95 mm, etc. The radii R1 and R3 are at a tibial eminenceof the prosthesis 16, e.g., at an ACL-substitution member 18 of theprosthesis 16. In an exemplary embodiment, the radii R1 and R3 can eachbe about 10 mm, and the radii R2 and R4 can each be about 5 mm.

In another embodiment, a prosthesis can be configured to restrictmediolateral motion of the prosthesis's femoral component, which canprevent impinging, a PCL between the femoral component and theprosthesis's tibial post and can prevent impinging the tibial postagainst femoral bone. An exemplary embodiment of such a prosthesis isillustrated in FIGS. 1F and 1G in which a central eminence portion 216of a tibial articular surface adjacent a post 222 of a tibial insert 218substantially conforms to a surface of a femoral implant 220 mateable tothe tibial insert 218. This substantial, conformity can restrictmediolateral motion of the femoral implant 220 and thereby preventimpingement of a PCL and/or femoral bone against the post 222.

Embodiments of prostheses described herein can be configured to be fixedto a patient's tibia, which can facilitate healing and/or functionalityof the prosthesis. In one embodiment, the prosthesis can be configuredto be directly fixed to a tibia using bone cement. As will beappreciated by a person skilled in the art, any bone cement can be usedto so affix the prosthesis. In another embodiment, the prosthesis can benonremovably coupled to a base, e.g., a biocompatible metallic base. Themetal base can be configured to be fixed to a tibia by using bone cementand/or by bone ingrowth or ongrowth at the bone/base interface. In yetanother embodiment, the prosthesis can be molded into a base, e.g., abiocompatible metallic base, by forming a monoblock implant. In stillanother embodiment, the prosthesis can be removably coupled to a base,e.g., a biocompadble metallic base using a locking mechanism. Thelocking mechanism can be configured to be actuated to affix theprosthesis to the base either during manufacture or intraoperativelyduring surgery.

In use, with the prosthesis implanted in a patient, during knee flexionfrom an extended position, the ACL-substitution member can be configuredto engage with the femoral notch structure, which can prevent thepatient's femur from displacing posteriorly, and can gradually guide thefemur's external rotation. In an exemplary embodiment, during kneeflexion from an extended position, anterior and lateral edges of theACL-substitution member can be configured to engage with anterior andlateral, edges of the femoral notch structure. With the prosthesisimplanted in the patient, during terminal extension from a flexedposition, the ACL-substitution member can be configured to engage withthe femoral notch structure, which can pull the patient's femur forward,and can gradually guide the femur's internal rotation. Generally, asillustrated in an embodiment shown in FIG. 1E, an ACL-substitutionmember 20 and a femoral notch structure 22 can be configured to engagethrough the full range of knee motion. The femoral notch structure 22 isshown in cross-section in FIG. 1E at different flexion angles. In anexemplary embodiment, this engagement can occur during only early kneeflexion, e.g., in a range of about −20° to 40°. In this way, theACL-substitution member and the femoral notch engagement can beconfigured to substitute for an absent, non-functional, or otherwisedamaged ACL ligament. The knee replacement prosthesis can also beconfigured to accommodate a patient's PCL. Because a patient's PCL canbe generally present and well-functioning in patients undergoing partialor total knee replacement surgery, the prosthesis can be implanted inthe patient while allowing the patient's PCL to remain and be functionalin the patient's body.

Knee replacement prostheses described herein can be configured to beused in partial knee replacement surgical procedures and in total kneereplacement surgical procedures. Exemplary embodiments of prostheses forboth types of procedures are discussed in turn below.

FIG. 2 illustrates an exemplary embodiment of a knee replacementprosthesis configured to provide substitution of an ACL in partial kneereplacement surgery. The prosthesis of FIG. 2 is a medial femoralprosthesis configured to resurface a medial tibial compartment. In FIG.2 showing the prosthesis implanted in a patient, the patient's PCLligament 24 is represented as a cylinder joining the tibial insertion ofthe ligament 24 to its insertion on the medial femoral condyle withinthe intercondylar region. As in the illustrated embodiment, theprosthesis can include a femoral implant 26, a tibial implant 28, anACL-substituting post 30, and a femoral notch structure 32. Theprosthesis shown in FIG. 2 is a medial prosthesis, but a lateralprosthesis can be configured similarly to the prosthesis of FIG. 2.Further, any medial prosthesis described herein can be similarlyconfigured as a lateral prosthesis, and vice versa. FIG. 3 illustratesan exemplary embodiment of a lateral knee replacement prosthesisincluding a femoral implant 34, a tibial implant 36, an ACL-substitutingpost 38, and a femoral notch structure 40 configured to providesubstitution of an ACL in partial knee replacement surgery and toresurface a lateral tibial compartment. FIG. 3 also represents thepatient's PCL ligament 42 as a cylinder.

The tibial implant 36 can have a variety of configurations. Although inthe illustrated embodiment the post 38 is integrally formed with thetibial implant 36, in some embodiments, the post 38 and the tibialimplant 36 can be discrete elements. If the post and the tibial implantare discrete elements, in any of the embodiments described herein, thepost can be configured to removably and replaceably couple to the tibialimplant. In this way, a kit can be provided including a plurality ofdifferent posts, e.g., posts having different sizes, being formed fromdifferent materials, etc., and a tibial implant configured to couple toeach of the different posts. Similarly, a kit can be provided includinga plurality of different tibial implants and one post, or a plurality ofdifferent posts, the one post or each of the plurality of posts beingconfigured to couple to any one of the tibial implants.

Generally, a medial tibial implant can be configured as a substitute fora medial tibiofemoral joint. As in the embodiment illustrated in FIGS.2, 4, and 5, the tibial implant 28 can have a shape substantiallyconforming to a shape of a medial tibial compartment, e.g., a medialsurface of a tibia 29. The tibial implant 28 can have a size, e.g., asurface area configured to face the medial tibial compartment,substantially similar to the medial tibial compartment such that thetibial implant 28 can be seated on the medial tibial compartment withoutextending beyond outside edges of the tibia 29 except for a portionextending over a portion of a lateral tibial compartment, e.g., alateral surface of the tibia 29. In other words, the tibial implant 28can have a size and shape such that the tibial implant 28 can be seatedon the tibia 29 with a first portion of the tibial implant 28 beingseated on or over the tibia's medial surface and a second, substantiallysmaller portion of the tibial implant being seated on or over thetibia's lateral surface.

The tibial implant 28 can have the post 30 coupled thereto near an edgethereof such that the post 30 can be positioned at a region near acenter of the proximal tibial bone, as also illustrated in FIGS. 4 and5, such that the post 30 can occupy a lateral portion of theintercondylar region. The post 30 coupled to the tibial implant 28 canhave a variety of configurations. As in the illustrated embodiment, thepost 30 can be asymmetric in sagittal, coronal, and transverse planes.For non-limiting example, with reference to the embodiment of thelateral prosthesis illustrated in FIG. 3, the tibial implant 36 of whichhaving the post 38 integrally formed therewith is also illustrated inFIGS. 6-8, 9, and 10, the post 38 can have an anteroposterior length ain a range of about 5 to 35 mm, e.g., in a range of about 10 to 20 mm,about 15 mm, etc. The prosthesis's post can have a mediolateral width bof in a range of about 5 to 25 mm, e.g., in a range of about 5 to 20 mm,in a range of about 5 to 15 mm, in a range of about 8 to 15 mm, about 9mm, etc. The post 38 can have a posterior height c in a range of about 1to 25 mm, e.g., in a range of about 5 to 20 mm, in a range of about 5 to15 mm, about 8 mm, etc. The post 38 can have an anterior height d in arange of about 3 to 25 mm, e.g., in a range of about 5 to 20 mm, in arange of about 8 to 15 mm, about 10 mm, etc. In some embodiments, thepost's anterior post height can be less than or equal to the post'sposterior post height. The post 38 can have a posterior slope in thesagittal view such that its height anteriorly, e.g., in a range of about8 to 15 mm, can be higher than its height posteriorly, e.g., in a rangeof about 5 to 10 mm.

The location of the post 38 relative to the tibial insert 36 can vary.For non-limiting example, with reference to the embodiment of thelateral prosthesis illustrated in FIGS. 9 and 10, a distance e from ananterior edge of the post to an anterior edge of the tibial base can bein a range of about 5 to 40 mm, e.g., in a range of about 10 to 30 mm,in a range of about 15 to 25 mm, about 22 mm, etc. A distance f from aposterior edge of the post 38 to the anterior edge of the tibial basecan be in a range of about 5 to 60 mm, e.g., in a range of about 15 to45 mm, in a range of about 30 to 40 mm, about 37 mm, etc. A distance gfrom a lateral edge of the post 38 to the lateral edge of the tibialbase can be in a range of about 10 to 50 mm, e.g., in a range of about15 to 45 mm, in a range of about 25 to 35 mm, about 30 mm, etc. Adistance h from a medial edge of the post 38 to the lateral edge of thetibial base can be in a range of about 15 to 60 mm, e.g., in a range ofabout 25 to 50 mm, in a range of about 35 to 45 mm, about 43 mm, etc.

In another exemplary embodiment, as illustrated in FIGS. 8A, 8B, and 8C,a tibial post 44 of a tibial insert 43 can be located substantiallyanterior to the tibial center, which can avoid potential impingement ofthe post 44 with a PCL ligament 46, which is illustrated as a cylinderin FIGS. 8A and 8C. Optionally, as illustrated in FIG. 8B, which shows afemoral component 45 of the prosthesis 43, a femoral intercondylar notch48 can be extended anteriorly to enable engagement of the femoral notch48 with the anteriorly located tibial post 44. A dotted line in FIG. 8Billustrates a conventional femoral intercondylar notch 48′.

In another exemplary embodiment, a tibial post can gradually blend intoa tibial insert, which can improve strength of the post. FIG. 11illustrates an exemplary embodiment of a prosthesis including agradually blending tibial post 50 adjacent a space 52 for a PCL.

In yet another exemplary embodiment, a lateral edge of a post can beextended back to a posterior edge of a tibial insert, which can increasetibial post strength. This embodiment can allow gradual tibialpost-femoral notch engagement from full flexion to extension, e.g., 155°to e.g., about 160°, and gradual disengagement from extension toflexion, e.g., −20° to 155°, e.g., about 160°. FIG. 12 illustrates anexemplary embodiment of a prosthesis including a tibial insert havingsuch an extending post 54. In an exemplary embodiment, an anterior widthi of the post 54 can be in a range of about 3 to 25 mm, e.g., in a rangeof about 10 to 20 mm, about 15 mm, etc.; a central width j of the post54 can be in a range of about 3 to 25 mm, e.g., in a range of about 5 to15 mm, about 8 mm, etc.; and a length k of the post 54 can be in a rangeof about 5 to 35 mm, e.g., in a range of about 15 to 30 mm, about 28 mm,etc. FIG. 12 shows a base profile 56 of the tibial insert by dottedoutline, with a space 58 for a PCL (not shown) being located adjacentthe post 54.

Referring again to the embodiment of FIG. 2, the femoral implant 26 andthe femoral notch structure 32, also shown in FIGS. 13 and 14, can alsohave a variety of configurations. The tibial implant 28 can articulateagainst, e.g., relative to, the femoral implant 26, and theACL-substituting tibial post 30 can articulate against the femoral notchstructure 32. The prosthesis shown in FIGS. 2, 13, and 14 is a medialprosthesis, but similar to that mentioned above, a lateral prosthesis,such as an embodiment shown in FIGS. 13A and 14A, can be configuredsimilarly to the prosthesis of FIGS. 2, 13. and 14. FIGS. 13A and 14Aillustrate an exemplary embodiment of a lateral knee replacementprosthesis including, a femoral implant 33, a tibial implant 35 attachedto a tibia bone 41, an ACL-substituting post 37, and a femoral notchstructure 39.

Although in the illustrated embodiment of FIGS. 2, 13, and 14 thefemoral notch structure 32 is integrally formed with the femoral implant26, in some embodiments, the femoral notch structure and the femoralimplant can be discrete elements. FIGS. 15 and 16 illustrate anexemplary embodiment of a prosthesis including a discrete femoral notchstructure 56 and a discrete femoral implant 58. Such a discrete femoralnotch structure 56 can be independently mounted on the femoral bone. Atibial implant 60 in the embodiment of FIGS. 15 and 16 can articulateagainst the femoral implant 58, and an ACL-substituting tibial post 62coupled to a tibia bone 64 can articulate against the femoral notchstructure 56 that is independently mounted on the femoral bone.

In addition to articulating against a tibial post, a femoral notchstructure can be configured to prevent the post from impinging on thelateral femoral bone through the full range of knee flexion, e.g.,between extended and flexed positions of the knee. In an exemplaryembodiment, a height of the femoral notch structure can be configured toprevent such impingement, such as by being in a range of about 1 to 30mm, e.g., in a range of about 2 to 15 mm, in a range of about 1 to 20mm, in a range of about 5 to 15 mm, about 10 mm, etc. FIGS. 17 and 18illustrate an exemplary embodiment of a lateral prosthesis in which aheight L of a femoral notch structure 66 of a prosthesis is configuredto prevent a tibial post from impinging on the lateral femoral bonebetween an extended position (FIG. 18) and a flexed position (FIG. 17).The notch structure's height L can be in a range of about 1 to 30 mm,e.g., in a range of about 5 to 15 mm, in is range of about 1 to 20 mm,about 10 mm, etc. In the embodiment shown in FIGS. 17 and 18, the notchstructure 66 is separate from the femoral implant such that it isconfigured to be independently mounted to a femoral bone, but asmentioned above, a notch structure can be integrally formed with afemoral implant. Alternatively or in addition to a height of a femoralnotch structure, an edge of a tibial post can be configured to preventthe post from impinging on the lateral femoral bone through the fullrange of knee flexion. As in an exemplary embodiment illustrated inFIGS. 19 and 20A, a lateral edge of an ACL-substituting tibial post 68of a tibial insert of a lateral prosthesis can be rounded at a tip 68 athereof at a radius r, and a height of the post 68 can be configured toavoid impingement with lateral femoral bone 70. Being rounded at the tip68 a can allow the tibial post 68 to avoid impingement with the lateralfemoral bone 70. The radius r can be, e.g., in a range of about 2 to 25mm. FIGS. 19 and 20A also show the tibial insert coupled to a femoralcomponent 72. FIG. 20B illustrates another embodiment of a lateral edgeof an ACL-substituting tibial post 76 of a tibial insert of a lateralprosthesis that can be chamfered or cut at an angle γ. At a tip 76 athereof The angle γ can be in a range of about 5 to 70°. Being chamferedor angled at the tip 76 a can allow the tibial post 76 to avoidimpingement with the lateral femoral bone. FIG. 20B also shows thetibial insert coupled to a femoral component 74.

Alternatively or in addition to a height of a femoral notch structureand/or an edge of a tibial post, the lateral femoral condyle bone can becontoured during surgery to prevent the post from impinging, on thelateral femoral bone, e.g., bone overhanging into the femoral notch,through the full range of knee flexion. As will be appreciated by aperson skilled in the art, the lateral femoral condyle bone can becontoured in a variety of ways, such as by using a bone shaping tool,e.g. a burr, a reciprocating saw, etc. In an exemplary embodiment, thebone shaping tool has a geometry configured to match the femoralcomponent's intercondylar notch, which can help ensure clearance of bonein the intercondylar region. FIGS. 20C and 20D illustrate embodiments ofsuch bone shaping tools 297, 298, with the bone shaping tool 299 of FIG.20D being shown adjacent to a femoral component 299 having anintercondylar notch with matching geometry to the tool 299.

A prosthesis can include one or more guiding slots configured tofacilitate the bone contouring, e.g., by providing adequate clearancefor tool(s) used to contour the bone and/or by providing adequate bonyunder hang (e.g., under hang in a range of about 1 to 5 mm). The one ormore guiding slots can be formed in a femoral component of a prosthesisor in a femoral trial component inserted into a patient prior toimplantation of a femoral component and, in an exemplary embodiment, caninclude at least one guiding slot in a lateral portion of the femoralcomponent. FIG. 20E illustrates an embodiment of a femoral trialcomponent 292 including two guiding slots 293 a, 293 b in a lateralportion of the femoral trial component 292, although any number of slotscan be provided. If multiple guiding slots are provided, the guidingslots 293 a, 293 b can intersect one another, which can allow a tool tosmoothly transition between slots oriented at different angles in thefemoral trial component 292. In some embodiments, a trial tibial insertcan include a tibial post having a larger size than a tibial postcoupled to a tibial insert to be implanted after the “trial” insertionof the trial tibial insert, which can help ensure that enough bone hasbeen cleared so as to not impinge bone against the tibial post coupledto the tibial insert to be implanted. FIGS. 20F and 20G illustrate anembodiment of a trial tibial post 294 of a tibial insert that has alarger size than a tibial post 294 a of a tibial insert to be implanted.FIG. 20G shows the trial tibial post 294 adjacent a femoral component295 and a femoral bone 296.

The femoral intercondylar notch can have a profile substantiallymatching that of a tibial post. Substantially matching the profiles ofthe femoral intercondylar notch and the post can allow the post to guidefemoral rotation and can maintain continuous contact with the femoralnotch even if the femoral component is rotationally mal-aligned withrespect to the tibia. As discussed above, the medial edge of an ACLsubstituting post can be contoured to avoid impingement with the PCL andcan have a generally curved or straight profile. As in an exemplaryembodiment illustrated in FIG. 21, a tibial post 78 of a lateralprosthesis and a lateral femoral intercondylar edge 80 can havesubstantially matching concentric circular profiles. In an exemplaryembodiment, a radius r5 of the circular profiles can be in a range ofabout 3 to 50 mm, e.g., in a range of about 5 to 30 mm, in a range ofabout 8 to 15 mm, about 10 mm, etc. In another exemplary embodimentillustrated in FIGS. 21A, 21B, 21C, and 21D, a contour of a medial edge77 a and a posterior edge 77 b of a tibial post 77 can be configured toprevent impingement of a PCL in the form of angled cuts. In an exemplaryembodiment, an angle θ of the posterior edge 77 b can be in a range ofabout 3° to 80°, and an angle ψ of the medial edge 77 a can be in arange of about 3° to 80°.

FIGS. 22-27 illustrate various embodiments of prostheses having postsand femoral intercondylar notches with substantially matching profiles.Generally, in these embodiments, an anterior edge of a tibial post has aconvex, concave, or flat profile and can engage with an anterior edge ofa femoral notch, which also has a convex, concave or flat profile. In anexemplary embodiment, a radius of the convex profile or the concaveprofile can be in a range of about 3 to 50 mm, e.g., in a range of about5 to 30 mm, in a range of about 8 to 15 mm, about 10 mm, etc. FIGS. 22and 23 illustrate a convex femoral notch 82 of a femoral component 86engaging with a tibial insert 88 with a tibial post 84 having a convexprofile. FIG. 24 illustrates an embodiment of a convex femoral notch 90engaging with a tibial post 92 having a concave profile. FIG. 25illustrates an embodiment of a concave femoral notch 94 engaging with atibial post 96 having a convex profile. FIG. 26 illustrates anembodiment of a convex femoral notch 98 engaging with a tibial post 100having a flat profile. FIG. 27 illustrates an embodiment of a flatfemoral notch 102 engaging with a tibial post 104 having a convexprofile.

FIGS. 28-33 illustrate various embodiments of prostheses having postsand femoral intercondylar notches with substantially matching profiles.Generally, in these embodiments, a tibial post occupies a lateralportion of the intercondylar region, and both a lateral edge of a tibialpost and a mating femoral notch can have a convex, concave, or flatprofile. In an exemplary embodiment, a radius of the convex profile orthe concave profile can be in a range of about 3 to 50 mm, e.g., in arange of about 5 to 30 mm, in a range of about 8 to 15 mm, about 10 mm,etc. FIGS. 28 and 29 illustrate an embodiment of a convex femoral notch108 of a femoral component 106 engaging with a tibial insert 110 with atibial post 112 having a concave profile. FIG. 30 illustrates anembodiment of a flat femoral notch 114 engaging with a tibial post 116having a flat profile. FIG. 31 illustrates an embodiment of a convexfemoral notch 118 engaging with a tibial post 120 having a convexprofile. FIG. 32 illustrates an embodiment of a convex femoral notch 122engaging with a tibial post 124 having a flat profile. FIG. 33illustrates an embodiment of a flat femoral notch 126 engaging with atibial post 128 having a convex profile.

As mentioned above, embodiments of prostheses described herein can beconfigured to substitute function of an ACL at least during early kneeflexion, such as by a tibial insert of the prosthesis including a tibialpost configured to eliminate abnormal posterior subluxation of the femurin early knee flexion. Conventional tibial insert articular surfacescan, however, have a relatively high anterior lip height, e.g., in arange from about 6 to 11 mm, which may hinder effectiveness of thetibial post in substituting ACL function. Thus, tibial insert articularsurfaces of prostheses described herein can have a lower anterior lipheight, e.g., in a range of about 0 to 6 mm, e.g., less than 6 mm, thanan anterior lip height in conventional tibial inserts. FIG. 68illustrates an embodiment of a tibial insert 224 having an anterior lipheight 224 h that is less than an anterior lip height 224 h′ of aconventional tibial insert 224′, shown by dotted line in FIG. 68. FIGS.69A and 69B illustrate an embodiment of a tibial insert 226 having ananterior radius 226 r, e.g., in a range of about 70 to 150 mm, that ishigher than an anterior radius, e.g., in a range of about 30 to 60 mm,of a conventional tibial insert, thereby allowing an anterior lip height226 h of the tibial insert 226 to be lower than an anterior lip heightof the convention tibial insert. The anterior radius 226 r of the tibialinsert 226 can be two or more times larger, e.g., over four timeslarger, than that of a conventional tibial insert. To allow for thelower anterior lip height 226 h, a low point 226 p of the tibial insert226 can be located more anteriorly than a low point of a conventionaltibial insert such that a distance 226D between the low point 226 p anda lateral edge of the tibial insert 226 can be greater than a distancebetween a low point and a lateral edge of the conventional tibialinsert. FIG. 70 illustrates an embodiment of a tibial insert 228 havinga lower anterior lip height than a conventional tibial insert by havingan intermediate radius 228 r, located between an anterior radius 228 r′and a posterior radius 228 r″ of the tibial insert 228, that can besubstantially larger than the anterior radius 228 f′. The intermediateradius 228 can be, e.g., in a range of about 70 to 300 mm, and theanterior radius 228 r′ can be, e.g., in a range of about 30 to 60 mm.The intermediate radius 228 of the tibial insert 228 can therefore betwo or more times larger, e.g., at about five times larger, than that ofa conventional tibial insert. In some embodiments, the intermediateradius 228 r can be substantially flat.

Medial and lateral anterior lip heights of a tibial insert can havedifferent heights to allow for ACL substitution at least during earlyknee flexion. In a normal knee, the ACL attaches to the lateral femoralcondyle and pulls the ACL more anteriorly on the tibia than the medialfemoral condyle. Thus, generally, an anterior medial lip height of atibial insert can be greater than an anterior lateral lip height of thetibial insert. Medial and lateral tibial insert profiles can bedifferent from one another to reflect this normal ACL function. FIG. 71illustrates an embodiment of a tibial insert 230 having a convex lateralprofile 230L and a concave medial profile 230M. These profile geometriescan result in an anterior medial lip height that is greater than ananterior lateral lip height by an amount 230D, e.g., greater by at least1 mm, e.g., in a range of about 1 to 10 mm. These profile geometries canallow the lateral femoral condyle to be located more anteriorly than themedial femoral condyle.

In some embodiments, an anterior edge of a tibial insert can extend atan angle relative to a base of the tibial insert, which can allow forACL substitution at least during early knee flexion by increasing atibiofemoral contact area during knee extension. The anterior locationof a femoral component on a tibia due to engagement of the femoralcomponent against the tibial insert's post can pull the femur forward onthe tibia. Thus, in extension and particularly in hyperextenstion, thefemoral component contacts the tibial insert at its anterior edge. Theangled anterior edge can therefore increase tibiofemoral contact. FIG.72 illustrates an embodiment of a tibial insert 232 having an anterioredge 232A extending at a non-zero angle a relative to a base 232B of thetibial insert 232 such that the anterior edge 232A extends anteriorly atthe non-zero angle α. The angle α can be up to about 30°, e.g., about15°, up to about 5°, in a range of about 5° to 10°, in a range of about10° to 20°, in a range of about 20° to 30°, etc.

Instead of reducing an anterior lip height of a tibial insert ascompared to a conventional tibial insert, a distal femoral condyleradius of a femoral implant can be reduced as compared to a conventionaltibial insert, thereby allowing a prosthesis including the femoralimplant to substitute function of an ACL at least during early kneeflexion. FIG. 73 illustrates an embodiment of a tibial insert 234 havinga reduced distal femoral condyle radius 234 r. The distal femoralcondyle radius 234 r is medial in the illustrated example, but similarto that mentioned above regarding medial/lateral prostheses, a distalfemoral condyle radius of a tibial insert can be lateral, therebyallowing an anterior lip height 234 h of the tibial insert 234 to begreater than or equal to an anterior lip height of the convention tibialinsert, and still allow for ACL substitution function withoutimpediment. To allow for the greater anterior lip height 234 h, a lowpoint 234 p of the tibial insert 234 can be located more posterior thana low point of a conventional tibial insert such that a distance 234Dbetween the low point 234 p and a lateral edge of the tibial insert 234can be greater than a distance between a low point and a lateral edge ofthe conventional tibial insert.

As mentioned above, prostheses described herein can be configured foruse in total knee replacement surgical procedures. Generally, total kneereplacement prostheses can be configured similarly to the partial kneereplacement prostheses discussed above and variously illustrated inFIGS. 2-33 and 68-73 except that the total knee replacement prosthesescan be configured to resurface both a medial tibial compartment and alateral tibial compartment. In other words, a total knee replacementprosthesis can be configured to be seated on the medial and lateraltibial compartment to provide total knee replacement and an ACLsubstitution. Like-named elements of partial knee replacement prosthesesand total knee replacement prostheses discussed herein can generally besimilarly configured.

FIG. 34 illustrates an exemplary embodiment of a knee replacementprosthesis configured to provide substitution of an ACL in total kneereplacement surgery. As in the illustrated embodiment, the prosthesiscan include a femoral implant 130, a tibial implant 132, and anACL-substituting post 134. The tibial implant 132 can include a space136 adjacent the post 134 configured to accommodate a PCL (not shown). Aprosthesis configured for total knee replacement surgery can alsoinclude a femoral component 140 including a femoral notch structure 138,such as in an exemplary embodiment illustrated in FIGS. 35 and 36. FIGS.35 and 36 show the femoral component 140 coupled to a tibial insert 142including a tibial post 144, and FIG. 35 shows a posterior view of thefemoral component 140 coupled to a femoral bone 146 and the prosthesisseating a PCL 148, which is illustrated as a cylinder.

FIG. 37 illustrates a posterior view of the prosthesis of FIG. 34 in usewith the patient's PCL ligament 131 being represented as a cylinderjoining the tibial insertion of the ligament 131 to its insertion on themedial femoral condyle within the intercondylar region. FIG. 38 showsthe prosthesis and PCL ligament 131 of FIG. 37 with the PCL ligament 131in different positions corresponding to different knee flexion anglesbetween about 0° to 70°. FIGS. 39-43 illustrate the tibial implant 132of the prosthesis of FIG. 34 and variously include reference charactersa1, b1, c1, d1, e1, f1, g1, and h1 respectively corresponding to length,width, posterior height, anterior height, and distances of the post 134similar to that discussed above with reference to FIGS. 6-10. As shown,for example, in FIGS. 42 and 43, the tibial implant 132 in a total kneereplacement prosthesis can be generally kidney-shaped to substantiallymatch the tibial surfaces to which it can be affixed.

FIGS. 44 and 45 illustrate exemplary embodiments of total kneereplacement prostheses that are respectively similar to the embodimentsof FIGS. 11 and 12 discussed above. FIG. 44 illustrates an exemplaryembodiment of a prosthesis including a gradually blending tibial post150 adjacent a space 152 for a PCL. FIG. 45 illustrates an exemplaryembodiment of a prosthesis including a tibial insert having an extendingpost 154, the post 154 having an anterior width i1, a central width j1,and a length k1. FIG. 45 shows a base profile 156 of the tibial insertby dotted outline, with a space 158 for a PCL (not shown) being locatedadjacent the post 154.

As discussed above, a notch structure and/or a post can be configured toprevent the post from impinging on the lateral femoral bone through thefull range of knee flexion. FIG. 46 illustrates an exemplary embodimentof a prosthesis having a tibial insert 162 having a post 160 with aheight configured to avoid impingement with the lateral femoral condyle.The prosthesis can also include a femoral component 164 adjacent afemoral bone 166. The patient's PCL ligament 168 is represented as acylinder. FIGS. 47 and 48, similar to FIGS. 19 and 20A, illustrate anexemplary embodiment of a prosthesis having a lateral edge of anACL-substituting tibial post 170 of a lateral prosthesis rounded on top.FIGS. 47 and 48 also illustrate a femoral component 172 mated to atibial insert 174 that includes the post 170. FIGS. 49 and 50, similarto FIGS. 17 and 18, illustrate an exemplary embodiment of a prosthesisin which a height L1 of the prosthesis's notch structure 176 can beconfigured to prevent a post 178 of a tibial implant 180 from impingingon the lateral femoral bone between an extended position (FIG. 49) and aflexed position (FIG. 50). The height L1 of the notch structure 176 canbe in a range of about 1 to 20 mm, in a range of about 5 to 15 mm, about10 mm, etc.

Similar to that discussed above, a femoral intercondylar notch of atotal knee replacement prosthesis can have a profile substantiallymatching that of the prosthesis's post. FIG. 21 also illustrates anexemplary embodiment of a tibial post of a total knee replacementprosthesis having a concentric circular profile substantially matchingconcentric circular profile of anterior and lateral surfaces of thefemoral intercondylar notch structure. FIGS. 23-27 discussed above alsoillustrate exemplary embodiments of prostheses having posts and femoralintercondylar notches with substantially matching profile, where theembodiment of FIG. 23 shows a sagittal cross section of an embodiment ofa total knee replacement prosthesis 182 illustrated in FIG. 51 thatincludes a femoral component 184 and a tibial insert 186. The prosthesis182 of FIG. 51 includes a convex tibial post 188 and a convex femoralintercondylar notch 190. Similar to FIGS. 28-33 discussed above,respectively, FIGS. 52-57 illustrate various embodiments of total kneereplacement prostheses having posts and femoral intercondylar notcheswith substantially matching profiles. FIG. 52 illustrates one embodimentof a total knee replacement prosthesis having a tibial insert 192 with aconcave tibial post 194 and a femoral component 196 with a convexfemoral intercondylar notch 198. FIG. 53 is a coronal planecross-sectional view of the prosthesis of FIG. 52 attached to a tibia.FIG. 54 illustrates one embodiment of a total knee replacementprosthesis attached to a tibia and having a flat tibial post 200 and aflat femoral intercondylar notch 202. FIG. 55 illustrates one embodimentof a total knee replacement prosthesis attached to a tibia and having aconvex tibial post 204 and a convex femoral intercondylar notch 206.FIG. 56 illustrates one embodiment of a total knee replacementprosthesis attached to a tibia and having a flat tibial post 208 and aconvex femoral intercondylar notch 210. FIG. 57 illustrates oneembodiment of a total knee replacement prosthesis attached to a tibiaand having a convex tibial post 212 and a flat femoral intercondylarnotch 214.

In addition to a prosthesis for total knee replacement being configuredfor ACL substitution, the prosthesis can be configured for PCLsubstitution. Providing a substitute for a PCL with a knee replacementprosthesis can help reduce a number of surgical procedures needed torepair the knee and/or can help the knee's functionality approach 100%after surgery. Generally, PCL and ACL substituting total kneereplacement prostheses can be configured similarly to ACL-onlysubstituting knee replacement prostheses discussed herein except thatthe PCL and ACL substituting total knee replacement prostheses can beconfigured for ACL substitution via engagement of an anterior surface ofthe prosthesis's tibial post with the anterior femoral intercondylarnotch. In contrast, a conventional prosthesis substitutes PCL functionvia the engagement of a posterior femoral cam and a posterior surface ofa tibial post. FIGS. 74A and 74B illustrate an embodiment of an ACL andPCL substituting total knee replacement prosthesis including a femoralcomponent 236 including a PCL substituting cam 236 p and an ACLsubstituting cam 236 a, and a tibial insert including a tibial post 238.Because of the absence of the PCL, an intercondylar notch of the femoralcomponent 236 can have a relatively large surface area configured tomate with the tibial post's geometry, as shown in FIGS. 74A and 74B,thereby allowing contact stresses at the mating interface to be reduced.In some embodiments, such as in an embodiment illustrated in FIG. 75,this relatively large surface area can be achieved by a thickness 240 t,e.g., a thickness in a range of about 4 to 10 mm (e.g., greater than 5mm), of a femoral notch 240 of a femoral component being greater than athickness, e.g., in a range of about 2 to 5 mm, of a femoral notch in aconventional femoral component, and by a radius 240 r, e.g., in a rangeof about 5 to 30 mm, of the femoral notch 240 being greater than aradius, e.g., in a range of about 2 to 5 mm, of a femoral notch in aconventional femoral component. In other embodiments, such as in anembodiment illustrated in FIG. 76A, this relatively large surface areacan be achieved without increasing thickness 242 t but by a radius 242r, e.g., in a range of about 5 to 30 mm, of a femoral notch 242 beinggreater than a radius, e.g., in a range of about 2 to 5 mm, of a femoralnotch in a conventional femoral component.

Tibial posts of prostheses configured to substitute ACL and PCL functioncan have a variety of profiles. As in one embodiment shown in FIG. 77, atibial post 244 can have a convex profile in a top-down view, which canbe configured to engage a rounded geometry of a femoral notch 246 of afemoral component. The convex profile of the post 244 can have a radius244 r, e.g., in a range of about 5 to 60 mm. A posterior surface 244 pof the post 244 can have a flat profile configured to engage with a flatposterior femoral cam. In another embodiment, shown in FIG. 78, anteriorand posterior surfaces of a tibial post 248 can have a convex profileconfigured to engage with a concave profile of a femoral intercondylarnotch 250 and a posterior femoral cam 252. The convex profile of thepost 248 can have a radius 248R, e.g., in a range of about 5 to 60 mm.In yet another embodiment, shown in FIG. 79, a tibial post 250 can havean angled posterior surface 250 p configured to engage a posteriorfemoral cam 252 and configured to allow asymmetric posterior motions ofthe medial and lateral condyles. In a sagittal view, anterior andposterior surfaces of an ACL and PCL substituting post can be angled.The angles of the surfaces can both be anterior, both be posterior, orone of each. The angle degree of the surfaces can vary, such as being apositive angle up to about 15°. FIG. 80A illustrates one embodiment of apost 254 that is posteriorly sloped relative to a base 254 b of a tibialinsert including the post 254, which includes posteriorly slopedposterior and anterior surfaces 254 a, 254 p. FIG. 80B illustrates oneembodiment of a post 256 that is anteriorly and posteriorly slopedrelative to a base 256 b of a tibial insert including the post 256,which includes a posteriorly sloped posterior surface 256 p and ananteriorly sloped anterior surface 256 a.

In any of the prosthesis embodiments disclosed herein, a tibial insertcan be in a fixed, non-variable position relative to a tibial base suchthat a post coupled to the tibial insert, whether the post is integralwith the tibial insert or is a discrete element from the tibial insert,can be in a fixed, non-variable position relative to the tibial base.Alternatively, in any of the prosthesis embodiments disclosed herein,particularly in total knee replacement prostheses, the a tibial insertcan be in non-fixed, non-variable positions relative to a tibialbaseplate. In other words, a prosthesis can be a mobile bearing implantin which the tibial insert is not in a fixed, non-variable positionrelative to the prosthesis's tibial base.

As in an embodiment illustrated in FIG. 81A, 81B, and 81D, a mobilebearing tibial insert 258 of a total knee replacement prosthesis caninclude a base, e.g., a baseplate 260, a medial tibial insert 262fixedly coupled to the baseplate 260, and a lateral tibial insert 264movably coupled to the baseplate 260 such that the lateral tibial insert264 can move relative to the baseplate 260 and to the medial tibialinsert 262. A tibial post 266 can be coupled, either integrally or as adiscrete element, to the medial tibial insert 262. The lateral tibialinsert 264 can therefore be movable relative to the post 266. Thelateral tibial insert 264 can be movably coupled to the baseplate 260 ina variety of ways, such as by a rail/track system. The baseplate 260includes an anterior-posterior rail 268, as shown in FIGS. 81A and 81D,and the lateral tibial insert 264 includes a rail 270, but the baseplate260 could include a rail with the lateral tibial insert including atrack. The rail/track in the illustrated embodiment has a T-shapedcross-section, but a rail/track system can have any cross-sectionalshape. The lateral tibial insert 264 can be configured to besubstantially conforming to a mating lateral femoral condyle, as shownin FIG. 81B. FIG. 81B also shows movable motion of the lateral tibialinsert 264 relative to the baseplate 260 and the post 266 with thelateral tibial insert 264 in solid line in a first position and indotted line in a second, different position. Only two differentpositions of the lateral tibial insert 264 is shown in FIG. 81B, but thelateral tibial insert 264 can be movable between any number of positionsrelative to the baseplate 260 and the post 266. A surface 260 s of thebaseplate 260, e.g., a top surface, to which the inserts 262, 264 can becoupled can have a convex profile in a sagittal view, as shown in FIG.81B. The baseplate's convex profile can have a radius 260 r, e.g., in arange of about 20 to 200 mm, in a range of about 60 to 200 mm, in arange of about 20 to 100 mm, etc. Alternatively, as shown in FIG. 81C, asurface 260 s' of a baseplate 260′ to which medial and lateral tibialinserts can be coupled can be substantially flat in a sagittal view. Atibial baseplate 275 including a substantially flat baseplate surfacecan, as shown in one embodiment in FIG. 81E, be movably coupled to atibial insert by including opposed side rails 272 that define a channel274 in which the tibial insert 276 can move. Similarly, a tibialbaseplate 275 a including a convex baseplate surface 275 b can, as shownin one embodiment in FIG. 81F, be movably coupled to a tibial insert byincluding one side rail 272 a that defines an interior guide surfacealong which a tibial insert 276 a can move.

Although a tibial post can be coupled to a tibial insert coupled to abaseplate in a mobile beating implant as discussed above, in anotherembodiment, a tibial post can be coupled to a baseplate, eitherintegrally or as a separate element, while medial and/or lateral tibialinserts coupled to the baseplate can be movably coupled to thebaseplate. In an exemplary embodiment, both the medial and lateraltibial inserts can be movably coupled to the baseplate. FIG. 82Aillustrates one embodiment of a tibial baseplate 278 having a medialtibial insert 279 a movably coupled thereto, a lateral tibial insert 279b movably coupled thereto, and a tibial post 280 non-movably coupledthereto either integrally or as a separate element. The medial andlateral tibial inserts 279 a, 279 b can therefore each be movablerelative to the post 280 and relative to each other. The medial andlateral tibial inserts 279 a, 279 b can each be coupled to the baseplate278 in any way, same or different from one another, such as by beingmovable within respective tracks 281 a, 281 b formed in the baseplate278.

In another embodiment, similar to that discussed above regarding aprosthesis including a tibial post coupled to a tibial insert coupled toa baseplate in a mobile bearing implant, a movable medial or lateraltibial insert can be movably coupled to a baseplate having asubstantially flat top surface including opposed side rails defining achannel in which a tibial insert can move. The side rails for a lateraltibial insert can be a farther distance apart from one another than siderails for a medial tibial insert such that the medial tibial insert canbe configured to undergo less anteroposterior translation compared tothe lateral tibial insert. This movement can allow normal kinematicscharacterized by greater anteroposterior tibiofemoral motion in thelateral compartment of the knee. FIG. 82B illustrates an embodiment of abaseplate 281 including a substantially flat baseplate surface to whicha medial tibial insert 282 a and a lateral tibial insert 282 b can becoupled. The surface can include anterior-poster opposed side rails 283a spaced a distance 284 a apart from one another between which themedial tibial insert 282 a can move and anterior-poster opposed siderails 283 b spaced a farther distance 284 b apart from one anotherbetween which the lateral tibial insert 282 b. The side rails 283 a, 283b can therefore be configured as anterior-posterior stops, e.g., one 283a located posteriorly and the other 283 a located anteriorly and one 283b located posteriorly and the other 283 b located anteriorly, so as toallow their associated tibial insert to move within a defineanterior-posterior area.

In another embodiment, a baseplate can include a protruding convexmember on a top surface thereof configured to allow a tibial insertcoupled to the baseplate to pivot thereabout. In one embodimentillustrated in FIG. 82C, a baseplate 285 can include a protruding convexmember 286 about which a tibial insert 287, e.g., a medial tibialinsert, can pivot. The protruding convex member 286 can have arelatively small radius 286 r, e.g., in a range of about 3 to 30 mm. Byhaving a relatively small radius 286 r, the protruding convex member 286can allow the tibial insert 287 to have relatively limitedanteroposterior motion. FIG. 82C shows the tibial insert 287 in a solidline in a first position at one end of the insert's range of pivotalmotion and in a dotted line in a second position at the other end of theinsert's range of pivotal motion. FIG. 82D illustrates a baseplate 288including a convex surface 289 to which a tibial insert 290, e.g., alateral tibial insert, can mate and be movable relative thereto. Theconvex surface 289 can have a relatively large radius 289 r, e.g., in arange of about 50 to 200 mm, which can allow for greateranterior-posterior motion to occur than with a smaller radius. FIG. 82Dshows the tibial insert 290 in a solid line in a first position at oneend of the insert's range of pivotal motion and in a dotted line in asecond position at the other end of the insert's range of pivotalmotion. A baseplate including the relatively small radius protrudingconvex member 286 of FIG. 82C for a medial tibial insert and therelatively large radius convex surface 289 of FIG. 82D for a lateraltibial insert can allow for greater mobility of medial relative to alateral side of the tibia, which can allow for natural medial pivotkinetics.

EXAMPLES

The performance of an ACL-substituted CR prosthesis configured for totalknee replacement surgery was compared with that of a conventional CRimplant. Five different activities of a knee including the prosthesiswere simulated, namely lunge, deep knee bend, chair rise/sit, stairascent, and walking. These simulations were carried out using a VirtualKnee Simulator, available from LifeModeler® Inc. of San Clemente,Calif., and the motion of the medial and lateral flexion facet centers(FFC) were measured during each activity. In all simulations the ACLligament was absent, while the PCL ligament was present. During allsimulated activities, the ACL-substituted prosthesis showed kinematicsclose to that of healthy knees. In contrast, the conventional CRprosthesis showed abnormal posterior location of the femur at fullextension and abnormal anterior sliding during early to mid-flexion forall the simulated activities.

FIGS. 58-67 illustrate the prosthesis along with various graphicalresults of the comparisons. Generally, FIGS. 58-65 illustrate results ofsimulations for the lunge, deep knee bend, and chair rise/sit activitieswith reference to in vivo knee motion data for healthy subjectsvariously extracted from Johal et al., “Tibio-Femoral Movement In TheLiving Knee: A Study Of Weight Bearing And Non-Weight Bearing Knee,” JBiomech. 2005 February, 38(2):269-76; Komistek et al., “In VivoFluoroscopic Analysis Of The Normal Human Knee,” Clin Orthop Relat Res.2003 May, (410):69-81; and Moro-oka, et al., “Dynamic ActivityDependence Of In Vivo Normal Knee Kinematics,” J Orthop Res. 2008 April,26(4);428-34. Generally, FIGS. 66 and 67 illustrate graphs showingresults of simulated walking with reference to in vivo knee motion datafor patients who received bi-unicondylar implants that preserve both theACL and PCL ligaments extracted from Banks et al., “Comparing In VivoKinematics Of Unicondylar And Bi-Unicondylar Knee Replacements,” KneeSurg Sports Traumatol Arthrosc. 2005 October, 13(7):551-6.

FIGS. 58 and 59 illustrate graphical results of motion during, simulatedlunge activity, one cycle of flexion from 0° to 120° and one cycle ofextension from 120° to 0°, with reference to healthy subject data fromJohal et al., referenced above. FIG. 58 shows the motion of the medialFFC 300 as a function of knee flexion angle during a lunge activity. Themedial FFC in the conventional CR implant was shifted posteriorly atfull extension and showed abnormal anterior sliding in early tomid-flexion, e.g., from 0° to 50°. In contrast, the ACL-substituted CRprosthesis showed more normal medial FFC motion, with minimalanterior-posterior translation until 90° flexion followed by posteriortranslation at higher flexion angles. FIG. 59 shows the motion of thelateral FFC 302 as a function of knee flexion angle during a simulatedlunge activity. The lateral FFC in the conventional CR implant was againshifted posteriorly at full extension and showed abnormal anteriorsliding during early to mid-flexion. In contrast, the ACL-substituted CRprosthesis showed kinematics very close to the in vivo kinematics ofhealthy knees.

FIGS. 60 and 61 illustrate graphical results of motion during simulateddeep knee bend activity, one cycle of flexion from 0° to 155° and onecycle of extension from 155° to 0°, with reference to healthy subjectdata from Johal et al., referenced above. FIG. 60 shows the motion ofthe medial FFC 304 as a function of knee flexion angle during a deepknee bending activity. The medial FFC in the conventional CR implant wasshifted posteriorly at full extension and showed paradoxical anteriorsliding in a mid-flexion range, e.g., from about 0° to 55°. In contrast,the ACL-substituted CR prosthesis showed more normal medial FFC motion,with minimal anterior-posterior motion until 85° flexion followed byposterior translation at higher flexion angles. FIG. 61 shows the motionof the lateral FFC 306 as a function of knee flexion angle during asimulated deep knee bending activity. The lateral FFC in theconventional CR implant was again dislocated posteriorly at fullextension and showed paradoxical anterior sliding in the mid-flexionrange. On the other hand, the ACL-substituted CR prosthesis showedkinematics closely mimicking the in vivo kinematics of healthy knees.

FIGS. 62 and 63 illustrate graphical results of motion during simulatedrising from and sitting into a chair, one full cycle from 10° to 105°flexion and from 10° to 105° flexion, with reference to healthy subjectdata from Komistek et al., referenced above. Similar to the lunge anddeep knee bending activities, the medial FFC of the conventional CRprosthesis again showed abnormal posterior location and anterior slidingduring a simulated chair rise/sit activity, as shown in FIG. 62. Themotion of the medial FFC 308 for the ACL-substituted CR prosthesis wasmuch more consistent with the in vivo data. Like the medial FFC, thelateral FFC for the conventional CR prosthesis showed abnormal posteriorlocation at full extension followed by anterior sliding, as shown inFIG. 63. In contrast, the lateral FFC 310 of the ACL-substitutedprosthesis showed posterior rollback of the lateral FFC consistent within vivo data.

FIGS. 64 and 65 illustrate graphical results of motion during simulatedstair ascent, one full cycle from 0° to 90° flexion and from 90° to 0°flexion, with reference to healthy subject data from Moro-oka et al.,referenced above. FIG. 64 shows that during the simulated stair ascent,the medial FFC of the conventional CR prosthesis showed abnormalposterior location at full extension, followed by anterior sliding. Themotion of the medial FFC 312 motion for the ACL-substituted CRprosthesis was much more stable, although it did not show the posteriorrollback seen in the in vivo data. Like the medial FFC, the lateral FFCfor the conventional CR prosthesis also showed abnormal posteriorlocation at full extension followed by anterior sliding, as shown inFIG. 65. In contrast, the lateral FFC 314 of the ACL-substitutedprosthesis showed posterior rollback consistent with in vivo data.

FIGS. 66 and 67 illustrate graphical results of motion during simulatedwalking, one full gait cycle going from 0° to 65° flexion and from 65°to 0° flexion, with reference to data from Banks et al., referencedabove. FIG. 66 shows the motion of the medial FFC as a function of kneeflexion angle during simulated walking. The medial FFC in theconventional CR implant was located posteriorly at full extension andshowed significant anterior sliding during flexion. In contrast, theACL-substituted CR prosthesis showed more stable medial FFC 316 motion,similar to that seen in vivo for patients with ACL and PCL preservingimplants. FIG. 67 shows the motion of the lateral flexion facet centeras a function of knee flexion angle during simulated walking. Thelateral FFC in the conventional CR implant was again located posteriorlyat full extension and showed abnormal anterior sliding with flexion. Incontrast, the ACL-substituted CR prosthesis showed lateral FFC 318motion similar to that seen in vivo for patients with ACL and PCLpreserving implants.

The devices disclosed herein can be designed to be disposed of after asingle use, or they can be designed to be used multiple times. In eithercase, however, the device can be reconditioned for reuse after at leastone use. Reconditioning can include any combination of the steps ofdisassembly of the device, followed by cleaning or replacement ofparticular pieces, and subsequent reassembly. In particular, the devicecan be disassembled, and any number of the particular pieces or parts ofthe device can be selectively replaced or removed in any combination.Upon cleaning and/or replacement of particular parts, the device can bereassembled for subsequent use either at a reconditioning facility, orby a surgical team immediately prior to a surgical procedure. Thoseskilled in the art will appreciate that reconditioning of a device canutilize a variety of techniques for disassembly, cleaning/replacement,and reassembly. Use of such techniques, and the resulting reconditioneddevice, are all within the scope of the present application.

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

What is claimed is:
 1. A medical device, comprising: a tibial implanthaving an inferior surface and an opposite, superior surface, theinferior surface being configured to be fixed to a tibia of a patient; afemoral implant mateable to the tibial implant and having an inferiorsurface and an opposite, superior surface, the superior surface beingconfigured to be fixed to a femur of the patient, and the tibial implantbeing configured to articulate relative to the femoral implant when thetibial implant is fixed to the tibia and the femoral implant is fixed tothe femur; a femoral intercondylar notch coupled to the femoral implant;and a post extending from the superior surface of the tibial implantnear an edge thereof such that the post simulates an anterior cruciateligament (ACL) when the tibial implant is fixed to the tibia and thefemoral implant is fixed to the femur, wherein a mediolateral distancemeasured from a medial or lateral surface of the post to an adjacentsurface of the femoral intercondylar notch is less than a secondmediolateral distance measured from the medial or lateral surface of thepost to an adjacent surface of the femoral intercondylar notch, thesecond measurement being taken at a more posterior location on the postthan the first measurement.
 2. The device of claim 1, wherein themediolateral distance is measured with the femoral component oriented ator near full extension relative to the tibia
 3. The device of claim 1,wherein the tibial implant has medial and lateral compartments, thelateral compartment being configured to be seated on a lateral surfaceof the tibia such that the lateral surface is substantially covered bythe lateral compartment, and the medial compartment being configured tobe seated on a medial surface of the tibia such that the medial surfaceis substantially covered by the medial compartment.
 4. The device ofclaim 1, wherein the post is integrally formed with the tibial implant.5. The device of claim 1, wherein the post is a discrete elementconfigured to couple to the tibial implant.
 6. The device of claim 1,wherein the post is configured to articulate relative to the femoralintercondylar notch.
 7. A medical device, comprising: a tibial implanthaving an inferior surface and an opposite, superior surface, theinferior surface being configured to be fixed to a tibia of a patient; afemoral implant rateable to the tibial implant and having an inferiorsurface and an opposite, superior surface, the superior surface beingconfigured to be fixed to a femur of the patient, and the tibial implantbeing configured to articulate relative to the femoral implant when thetibial implant is fixed to the tibia and the femoral implant is fixed tothe femur; and a post extending from the superior surface of the tibialimplant near an edge thereof such that the post simulates an anteriorcruciate ligament (AOL) when the tibial implant is fixed to the tibiaand the femoral implant is fixed to the femur, a medial or lateralsurface of the post being angled in the transverse plane away from theadjacent femoral intercondylar notch such that distance between the saidmedial/lateral surface of the post and the adjacent femoralintercondylar notch is greater at a posterior location than at ananterior location on the post,
 8. The device of claim 7, wherein themediolateral distance is measured with the femoral component oriented ator near full extension relative to the tibia
 9. The device of claim 7,wherein the tibial implant has medial and lateral compartments, thelateral compartment being configured to be seated on a lateral surfaceof the tibia such that the lateral surface is substantially covered bythe lateral compartment, and the medial compartment being configured tobe seated on a medial surface of the tibia such that the medial surfaceis substantially covered by the medial compartment.
 10. The device ofclaim 7, wherein the post is integrally formed with the tibial implant.11. The device of claim 7, wherein the post is a discrete elementconfigured to couple to the tibial implant.
 12. The device of claim 7,further comprising a femoral notch structure coupled to the femoralimplant, the femoral notch structure being configured to prevent thepost from impinging on a lateral surface of the femur through a fullrange of knee flexion when the tibial implant is fixed to the tibia andthe femoral implant is fixed to the femur, wherein the post isconfigured to articulate relative to the femoral notch structure.
 13. Amedical device, comprising: a tibial implant having an inferior surfaceand an opposite, superior surface, the inferior surface being configuredto be fixed to a tibia of a patient; a femoral implant mateable to thetibial implant and having an inferior surface and an opposite, superiorsurface, the superior surface being configured to be fixed to a femur ofthe patient, and the tibial implant being configured to articulaterelative to the femoral implant when the tibial implant is fixed to thetibia and the femoral implant is fixed to the femur; and a postextending from the superior surface of the tibial implant near an edgethereof such that the post simulates an anterior cruciate ligament (ACL)when the tibial implant is fixed to the tibia and the femoral implant isfixed to the femur, a medial and/or lateral surface of the post designedsuch that a mediolateral distance between a medial and/or lateralsurface of the post and a longitudinal plane is greater at a superiorlocation on the post than at an inferior location on the post, thelongitudinal plane being perpendicular to the transverse plane, andbeing oriented along a longitudinal length of the post measured along aline from an anterior edge to a posterior edge of the post.
 14. Thedevice of claim 13, wherein the mediolateral distance is measured withthe femoral component oriented at or near full extension relative to thetibia.
 15. The device of claim 13, wherein such a reduction inmediolateral distance at a superior location on the post relative to aninferior location begins at or below the level of a distal bonyresection of the medial/lateral femoral condyle.
 16. The device of claim13, wherein the post is integrally formed with the tibial implant. 17.The device of claim 13, wherein the post is a discrete elementconfigured to couple to the tibial implant.
 18. The device of claim 13,further comprising a femoral notch structure coupled to the femoralimplant, the femoral notch structure being configured to prevent thepost from impinging on a lateral surface of the femur through a fullrange of knee flexion when the tibial implant is fixed to the tibia andthe femoral implant is fixed to the femur, wherein the post isconfigured to articulate relative to the femoral notch structure.
 19. Amedical device, comprising: a tibial implant having an inferior surfaceand an opposite superior surface, the inferior surface configured to befixed to a tibia of a patient; a femoral implant mateable to the tibialimplant and having an inferior surface and an opposite superior surface,the superior surface configured to be fixed to a femur of the patient,and the tibial implant configured to articulate relative to the femoralimplant when the tibial implant is fixed to the tibia and the femoralimplant is fixed to the femur; and a post extending from the superiorsurface of the tibial implant near an edge thereof such that the postsimulates an anterior cruciate ligament (ACL) when the tibial implant isfixed to the tibia and the femoral implant is fixed to the femur;wherein a bone facing surface of the femoral component is raised near ananterior aspect of a femoral notch relative to surfaces near the medialand/or lateral aspects of the femoral notch.
 20. A medical device,comprising: a tibial implant having an inferior surface and an oppositesuperior surface, the inferior surface configured to be fixed to a tibiaof, a patient; a femoral implant mateable to the tibial implant andhaving an inferior surface and an opposite superior surface, thesuperior surface configured to be fixed to a femur of the patient, andthe tibial implant configured to articulate relative to the femoralimplant when the tibial implant is fixed to the tibia and the femoralimplant is fixed to the femur; and a post extending from the superiorsurface of the tibial implant near an edge thereof such that the postsimulates an anterior cruciate ligament (ACL) when the tibial implant isfixed to the tibia and the femoral implant is fixed to the femur ananterior surface of the tibial insert being angled anteriorly relativeto a plane perpendicular to the tibial insert base.